The invention relates to a system for the line-wise compression of binary data of a picture field in a compression device. The data is organized in a matrix of pixels. The system also decompresses the data, after the data passes through a medium, in order to reorganize the data so as to form the picture field. The system includes: a compression translator having an input for the data, a series length detector for detecting a series length of equivalent pixel bits for conversion into a series length indication which corresponds to the series length, and an output which is connected to said medium. A system of this kind is known from U.S. Pat. No. 4,622,585, issued Nov. 11, 1986 to Reitsma. The known device is suitable for black/white pictures and is optimized so as to achieve the largest possible compression factor. This requires a substantial data processing capacity.